The present invention relates to rocket motor assemblies generally, and more particularly, to a thrust reducing nozzle assembly for a rocket decoy.
Infrared-radiation decoys have been used to protect friendly aircraft from attack by enemy missiles. An effective decoy must match the radiation signature and flight parameters of the aircraft it is designed to protect. The intensity, wavelength and spacial distribution of radiation generated by the decoy must closely match that of the aircraft. Additionally, there are limitation on thrust levels.
Flares are one type of infrared-radiation decoy. Flares are pyrotechnic devices which burn at atmospheric pressure and produce a high-intensity point of radiation. However, since flares are non-propulsion devices, they do not escort the aircraft, but rather free-fall away from it. Accordingly, flares provide protection for only a short interval of time.
Rocket decoys can offer advantages over flares. Rocket type decoys are designed to generate thrust as opposed to a zero thrust flare. In this manner, the rocket decoy can fly behind and escort an aircraft over an extended period of time. However, it has been found that rocket decoys are limited by certain factors. These factors include the inability to achieve maximum combustion temperature (i.e., exhaust plume intensity) due to inadequate mixing of combustion species. This creates problems in simulating the exhaust plume of the aircraft to be protected. Additionally, the mass flow rate required to achieve the desired exhaust plume intensity can produce a thrust level too high for best performance. Specifically, an excessive thrust level can cause the decoy to overtake the aircraft it is intended to protect. One attempt to reduce the rocket thrust was to arrange the exhaust nozzles of the rocket motor assembly outboard, away from the flight center line to direct exhaust jets radially outward. However, this approach has been found to dissipate the exhaust flow, resulting in an undesirable reduction in exhaust plume intensity.
Thus, there is a need to provide a rocket motor assembly having a nozzle that facilitates increased combustion and exhaust plume temperatures, while enabling a thrust level reduction.